1. Field of the Invention
The present invention relates to a three-dimensional image display apparatus, and more particularly, to a multi-viewpoint three-dimensional image display apparatus with a diffractive optical device having a lenticular lens function. The present application is based on Korean Patent Application No. 2001-62356, filed Oct. 10, 2001, which is incorporated herein by reference.
2. Description of the Related Art
Three-dimensional image displays are largely classified into stereoscopic displays, multi-viewpoint displays, and volumetric displays.
A stereoscopic display uses binocular parallax. More specifically, a stereoscopic display shows two images to the respective left and right eyes so that the brain recognizes a three-dimensional image due to a binocular parallax. One approach for accomplishing a stereoscopic display is to create a three-dimensional image by wearing glasses, which is used in movie theatres and various events. For two images, viewers do not feel eye strain if there is no contradiction at vergence and the focal position. However, since the vergence and the focal position may be different due to different positions at which a viewer views images, the viewer feels eye strain when viewing stereoscopic images for a long period of time.
In a multi-viewpoint display, a plurality of images taken from different angles are displayed to allow a viewer to see a three-dimensional image. When a viewer moves, the image which the viewer is observing moves so that a plurality of viewers can observe the images. In addition, since different images taken from different angles are displayed, the contradiction of vergence and a focal position is less than in a stereoscopic display or may not occur at all. Accordingly, viewers feel less eye strain than when viewing a stereoscopic display.
In a volumetric display, a three-dimensional image can be recognized from an after-image in three dimensions. A volumetric display includes a method of rotating a display unit or screen and a method of reproducing beams of light using holograms, integral photography, or the like. In the volumetric display, the contradiction of vergence and a focal position does not occur, so viewers do not feel eye strain. However, complex optical mechanisms are required for the method of rotating a display unit or screen, and a panel having several hundreds or a thousand times higher resolution than usual panels is required for the method of reproducing beams of light.
A multi-viewpoint display includes lenticular methods and filter or slit methods.
FIG. 1 shows a lenticular method disclosed in International Patent Publication No. WO 99/5559. It shows a multi-viewpoint display using 7 viewpoints. Referring to FIG. 1, reference numeral 10 denotes a sub-pixel array on a panel, and reference numeral 12 denotes a sub-pixel. A number written within each of the sub-pixels 12 denotes the sequence of each of the 7 viewpoints. In case of color pixels, three consecutive sub-pixels having the same viewpoint number are red (R), green (G), and blue (B) sub-pixels and form a single color pixel. A slanted lenticular lens 14 is provided above the sub-pixel array 10. Sub-pixels 12 at a first row are arranged in order of 2, 4, 6, 1, 3, 5, and 7, and sub-pixels 12 at a second row are arranged in order of 1, 3, 5, 7, 2, 4, and 6. Two lenticular lenses 14 are provided above seven consecutive sub-pixels. When lines parallel to the slanted lenticular lenses 14 are drawn and processed from the left side to the right side of the panel, seven viewpoints can be sequentially viewed from sub-pixels 12 numbered 1 to sub-pixels 12 numbered 7. In other words, the sub-pixels 12 numbered 2 are connected along the dotted line A, the sub-pixels 12 numbered 2 and 3 are connected along the dotted line B, and the sub-pixels 12 numbered 3 are connected along the dotted line C.
However, in such a structure as shown in FIG. 1, there is a lenticular connection part 15 that crosses the sub-pixels 12. The sub-pixels, which are positioned at the lenticular connection part 15, are influenced by the two lenticular lenses 14 beside the lenticular connection part 15. Accordingly, a light beam is divided in two directions, so a dual image is shown when a three-dimensional image is displayed. Consequently, resolution is degraded. Moreover, when a two-dimensional image is displayed, the sub-pixels 12 at the lenticular connection part 15 do not serve to form an image, thus degrading resolution.